This is the driver for the Toshiba TX4939 SoC ATA controller.
This controller has standard ATA taskfile registers and DMA
command/status registers, but the register layout is swapped on big
endian. There are some other endian issue and some special registers
which requires many custom dma_ops/port_ops routines.
Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>